import tensorflow as tf


# place holder
input1 = tf.placeholder(tf.float32)
# 给定结构
# input1 = tf.placeholder(tf.float32，……)
input2 = tf.placeholder(tf.float32)

output = tf.mul(input1,input2)


#  place holder && feed_dict
with tf.Session() as sess:
    print(sess.run(output,feed_dict={input1:[7.],input2:[2.]} ))